In the field of toners for electrophotography, with the progress of electrophotographic systems, there has been demand to develop toners having enhanced storage stability, stability in the environment, image-transferability, etc.
Patent Document 1 discloses a method for hydrophobicizing the surfaces of chemical prepared toner particles, wherein, during production of a chemical prepared toner having a core/shell structure, shell particles are deposited on core particles through encapsulation without adding a metal salt.
Patent Document 2 discloses a method for improving the image-transferability and storage stability of a chemical prepared toner, wherein, during production of the chemical prepared toner, inorganic microparticles are caused to deposit on aggregated particles formed in advance, and the thus-modified particles are coalesced, to thereby form particles on which inorganic microparticles are uniformly deposited.
Meanwhile, chemical prepared toners encounter difficulty in receiving shear by mechanical means (e.g., kneading), resulting in poor dispersion. This impairs the storage stability of the toners. Thus, Patent Document 3 discloses a technique of employing two or more metal salts having different valencies as aggregating agents in the production of a chemical prepared toner, for attaining good storage stability and tribocharge stability in the environment.
Patent Document 4 discloses a method for producing a chemical prepared toner, wherein, in production of the chemical prepared toner, the aggregating agent concentration is caused to vary at hot-melt-bonding in order to attain satisfactory chargeability. Patent Document 5 also discloses a method for producing a chemical prepared toner, wherein, an aggregating agent having a valency of 2 or more is employed in production of the chemical prepared toner, in order to attain satisfactory image-transferability.